Scroll wheel zooms when using Loop Cut And Slide
Fortunately I stumbled over the solution for this. It has nothing to do with OS or how Blender is installed.

It's simple: If you click Loop Cut in the tool shelf, you get the crippled behaviour with scrolling and not being able to slide the new cut. But if you use Loop Cut And Slide with the shortcut Strg+R, it behaves as usual. I've tested it with Blender 2.79 and can confirm that you get the same behavior regardless of how you start the tool.